*{
  margin: 0;
  padding: 0;
}


.app{
  display: flex;
  color: rgb(113, 112, 112);
  .left{
    width: 100px;
    line-height: 40px;
    text-align: center;
    background-color: #dad9d9;
    height: 100%;
    .btn{
      height: 50px;
    }
    .btn.active{
      color: red;
      background-color: rgb(248, 246, 246);
      font-weight: bold;
    }
  }
  .right{
    flex:1;
    flex-wrap: wrap;
    display: flex;
    height: 100px;
    .item{
      width: 33%;
      height: 100px;
      text-align: center;
      img{
        width: 80%;
      }
    }
  }
}